Friday, 27 July 2012
Friday, 20 July 2012
A paper just out in PLoSOne reports that chimpanzees, given some experience and enough of a weight difference, prefer to use heavier hammer stones when cracking hard nuts. This is apparently quite exciting: this is the first study to isolate weight as a property relevant to the task of cracking open a nut.
This caught my attention because weight is not actually the only key property that determines nut cracking success. A heavy hammer is great, but it will eventually become too heavy to lift, and for a given size stone there may very well be an optimum weight (similar to how people choose very specific combinations of size and weight when asked to throw objects to a maximum distance; Zhu & Bingham, 2011). In the current experiment, when the only difference between the objects was weight, the chimpanzees often went to the heaviest stone because it took the fewest strikes and least time to crack the nut. But is this just an artefact of the current experiment? And if so, can an ecological approach find ways to find out just how chimps choose their tools?
Friday, 6 July 2012
One of Gibson's key contributions was to reveal that it was possible for the optic array to specify a meaningful property of the world. Gibson insisted that specification existed between the world and optics (each property produced one unambiguous pattern, and thus the mapping is 1:1). Specification, said Gibson, meant direct perception was possible, because picking up that one variable meant perceiving the one property that caused it.
Turvey, Shaw, Reed & Mace (1981) formalised this idea by describing how ecological laws governed which properties of the world could be specified and identifying that these laws allowed affordances into this set. Turvey et al (hence TSM, because Reed changed his mind later on) then insisted that, in order for perception to be direct, specification also had to exist between the optics and the perceiver; an organism should only use one variable per property, and thus the mapping from world to perceiver is 1:1:1. This is a very high bar, and was put in place to defend ecological psychology from the Establishment attack (Fodor & Pylyshyn, 1981).
Withagen & Chemero (2009) think that the 1:1:1 account is incompatible with evolutionary thinking, and they aren't hot on the 1:1 account either. Specifically, they think that any given species will show individual variation in it's members ability to use information, and that in many cases species will end up using sub-optimal solutions (two important elements of evolutionary thinking). The1:1:1 bar, they say, is implausibly high and a naturalised theory of perception (one that is compatible with evolution) will instead predict the common use of non-specifying information. They also claim that this does not stop perception from being direct, so long as you allow 'directness' to live along a continuum.
I think there are some important issues here, but I think this paper's presentation is problematic. It contains no analysis of any particular information or task, and instead is full of sentences such as 'it seems more plausible to us that' and 'it is possible that'. This comes off as the kind of woolly evolutionary thinking psychology is rightly scolded for. Gibson and TSM spent a lot of time trying to make us pay less attention to what might be and more to what is.My concerns are mostly along these lines, and once I get them off my chest I want to turn in future posts to some ideas for a research programme to pursue this all in more detail.
Wednesday, 4 July 2012
Michael Britt (@mbritt on Twitter) runs the popular Psych Files podcast, which is downloaded by thousands of students and interested people. A while back he invited us for an interview on embodied cognition, and we Skyped with him a few weeks ago. Our interview is now live, and available from his website and from iTunes.
We had a great time chatting to Michael and he's done a great job! Let us know what you thought in the comments :)